Chain saw

Abstract

A chain saw includes: a motor driven by electric power; a housing configured to accommodate the motor; a guide bar attached to the housing; a chain blade wound around the guide bar; a sprocket engaged with the chain blade to drive the chain blade, wherein the chain saw is configured to transmit a driving force of the motor to the sprocket via a clutch mechanism, wherein the chain saw comprises a shut-off switch for detecting an actuation of the clutch mechanism and is configured such that the power supply to the motor is stopped when the actuation of the clutch mechanism is detected by the shut-off switch so as to brake electrically. The electrical brake is provided together with a mechanical brake that is configured to work when a hand guard is rotated.

What is claimed is: 
     
       1. A chain saw comprising:
 a motor driven by electric power; 
 a housing configured to accommodate the motor; 
 a guide bar attached to the housing; 
 a chain blade driven by the motor and wound around the guide bar; 
 a sprocket engaged with the chain blade to drive the chain blade; 
 a trigger switch; and 
 a control device connected to the trigger switch and configured to control rotation of the motor,
 wherein a driving force of the motor is configured to be transmitted to the sprocket via a clutch mechanism, 
 wherein the chain saw comprises a clutch state detection unit configured to detect an actuation of the clutch mechanism, and 
 wherein the power supply to the motor is stopped when the actuation of the clutch mechanism is detected by the clutch state detection unit, 
 wherein the clutch state detection unit is connected to the control device, 
 wherein the control device is configured to shut off the power supply to the motor when an operation of the clutch state detection unit is detected by the control device, and 
 wherein the control device is configured to release the shut-off of the power supply upon detecting that the operation of the trigger switch is released after the shutoff of the power supply to the motor. 
 
 
     
     
       2. The chain saw according to  claim 1 , wherein the clutch state detection unit comprises a switch configured to switch between on and off states in accordance with the actuation of the clutch mechanism. 
     
     
       3. The chain saw according to  claim 1 , wherein the clutch mechanism comprises:
 first engagement portions formed at the sprocket; 
 a clutch member having second engagement portions corresponding to the first engagement portions of the sprocket and being configured to be urged by a spring to abut against the sprocket; and 
 a spindle coupled to the clutch member by a spline connection formed at an inner periphery of the clutch member and an outer periphery of the spindle to transmit a rotating force of the motor, and 
 wherein the power transmission from the clutch member to the sprocket is configured to be released when overload is applied to the chain blade and the clutch member slides in an axial direction of the spindle against an urging force of the spring. 
 
     
     
       4. The chain saw according to  claim 3 , wherein the clutch member comprises an actuation part at an outer periphery thereof, and
 wherein the actuation part is configured to move a plunger of the clutch state detection unit, which is arranged near the clutch member, when the clutch mechanism is actuated and the power supply to the motor is stopped. 
 
     
     
       5. The chain saw according to  claim 1 , further comprising:
 a hand guard provided at a side of the housing to which the chain blade extends and, 
 a brake device configured to suppress the rotation of the chain blade by pivoting the hand guard, 
 wherein the clutch mechanism is configured to be actuated when the brake device is actuated and the power supply to the motor is stopped. 
 
     
     
       6. The chain saw according to  claim 5 , wherein the brake device is configured to mechanically brake the sprocket. 
     
     
       7. A chain saw comprising:
 a motor driven by electric power; 
 a housing configured to accommodate the motor; 
 a guide bar attached to the housing; 
 a chain blade driven by the motor and wound around the guide bar; 
 a hand guard provided at a side of the housing to which the chain blade extends; 
 a mechanical brake configured to suppress the rotation of the chain blade by pivoting the hand guard; 
 an electrical brake configured to shut off the power supply to the motor when a strong external force is applied to the chain blade; 
 a sprocket engaged with the chain blade to drive the chain blade; 
 a trigger switch; and 
 a control device connected to the trigger switch and configured to control rotation of the motor,
 wherein the mechanical brake and the electrical brake are actuated independently of each other without being in conjunction with each other, 
 wherein a driving force of the motor is configured to be transmitted to the sprocket via a clutch mechanism, 
 wherein the chain saw comprises a clutch state detection unit configured to detect an actuation of the clutch mechanism, 
 wherein the power supply to the motor is stopped when the actuation of the clutch mechanism is detected by the clutch state detection unit 
 wherein the clutch state detection unit is connected to the control device, 
 wherein the control device is configured to shut off the power supply to the motor when an operation of the clutch state detection unit is detected by the control device, and 
 wherein the control device is configured to release the shut-off of the power supply upon detecting that the operation of the trigger switch is released after the shutoff of the power supply to the motor.